Balanced rotary hydraulic valves



July 26, 1960 J. D. NORTH 2,945,343

BALANCED ROTARY HYDRAULIC VALVES Filed May 24, 1957 lNvENToR Jorm DunuzyNaRrH ATTORNEY BALANCED ROTARY HYDRAULIC VALVES John D. North, Eversley,Bridgnorth, Salop, England Filed May 24,1957, Ser. No. 661,345 Claimspriority, application Great Britain Jan; 2, 1957 7 Claims. (Cl.-137624)This invention relates to'hydraulic valves in hydraulic control systemsof the kind comprising a source of liquid under pressure, an actuatorsuch as a hydraulic jack or motor and a valve for connecting'one"or"other side of the actuator to the source of supply of liquidunder'pre'ssure and to a low pressure outlet respectively.

It is known to use for such purposes valves 'of'therotary type in whichacylindrical'rotor' or barrelfits Within a cylindrical casing and haschannels cut'in it'to' pro vide an adjustable means of communicationbetween ports formed in said casing.

It has previously been proposed to provide roller or ball hearings tosupport the valve in the casing to reduce friction when the valve isrotated. ItllS well known that the high pressure" ports'mustibesymmetrically arrangedso as tobalance" the "statici load'sfonthe bearings andto ensurethat this'pressure does no'fproduc'e a torquewhen the valve is closed.

It is further known that even when the valve is opened such staticforces can still be balanced but due to the Bernoulli forces arisingfrom the oil flow through the valve this balance is disturbed. Theobject of the pres ent invention is to provide an improved form ofconstruction of hydraulic valve in which said Bernoulli forces areminimized.

The invention accordingly provides in a hydraulic control system of thekind hereinbefore specified, a rotary hydraulic valve comprising twohigh pressure inlet ports, two low pressure outlet ports and two portsconnected to each side of a hydraulic actuator, the connecting channelsin the barrel of the valve being so arranged that when the valve isopened both high pressure inlet ports are connected to the twocorresponding actuator inlet ports but only one actuator port isconnected to one low pressure outlet port at any one time.

In order that the invention may be more clearly understood referencewill now be made to the accompanying drawings in which:

Fig. 1 is a longitudinal section of a known form of valve,

Fig. 2 is a section on the line II-II of Fig. 1,

Fig. 3 is a view similar to Fig. 1 of a hydraulic valve construction inaccordance with the present invention and showing the valve closed,

Fig. 4 is a section on the line IVIV of Fig. 3,

Fig. 5 is a view similar to Fig. 3 but showing the valve opened in onedirection,

Fig. 6 is a section on the line VI-VI of Fig. 5,

Fig. 7 is a view similar to Fig. 5 but showing the valve opened in theother direction, and

Fig. 8 is a section on the line VIIIVIII of Fig. 7.

Referring to Figs. 1 and 2 of the drawings, ports marked P are connectedto the high pressure source, the ports marked P are connected to returnfluid to the reservoir from which the high pressure source draws itssupply. The pair of ports marked A are connected to one side of theactuator and the pair of ports marked A to the other side. The grooves Gpermit fluid to States Patent flow from each of the pair of highpressure 'ports P to its corresponding member of the pair of actuatorinlet ports A or A according to the direction of rotation of the-valverSimilarly each of the pair of actuator outlet ports permits fluid topass from each member of the corresponding pair ofoutlet ports P to thelow pressure sink. It is well known that with this construction theBernoulli forces produce a torque on the valve, the said torquebein'grin the opposite direction to that in which the valve has-beenopened.

The'constructionaccording to the present invention is illustrated inFigs. 3 to 8. When the valve is opened each-member of the'pair of highpressure ports P is connected tothecorresponding member of the pair ofactuator inlet ports A- A or A A (as the case may be) but only one ofthe pair of actuator outlet ports A A'- or A A -is connected'to one ofthe low pressure outlet ports P at any one time, one member of the pairA Ag being' connected to one: P when the valve is rotated in onedirection, se'eJFigifi, and one member of'th'epair A A being connectedto the other port P when. the valve-is rotatedin. the oppositedirection, see Fig. -8. Moreover, the channels C and D in the barrelwhichpermit connection between the ports when the valve is openedaregiven-aconcave arcuate form. It has been found thatwithrthisconstruction the Bernoulli forces may be almost completelybalanced. Most satisfactory balance has been obtained when the anglebetween the centerline of the low pressure ports P and that of theactuator ports is substantially less than that between the centerlineof'th'e high pressure ports P and that of the actuator ports. It hasfurther been found that a circular arc with a camber of the order of 11%of the chord for the channel C under the high pressure ports and 10% ofthe chord for the channel under the low pressure ports D is an effectiveform. The invention is not however confined to this precise form.

The theory underlying the embodiments of the invention illustrated inFigs. 3 to 8 may be discerned by applying the well known laws of fluidflow to the specific passageways and ducts illustrated in these figures.In Fig. 6, for example, an analysis of the conditions in the channels Cindicate that by virtue of their configuration, the center of pressureapplied to the valve rotor results in a counterclockwise torque. This isevident from the fact that the center of pressure in channels C isdisplaced from the line of symmetry towards the port P in each channel.There is accordingly a counterclockwise torque associated with upperchannel C and a counterclockwise torque associated with lower channel C.Opposing these torques is a compensating torque developed by virtue ofthe fluid flow in left channel D. The center of pressure in this channelshifts towards port A thereby producing a clockwise torque. It is thusevident that the arrangement provides for a balancing of the Bernoulliforces.

A similar analysis of conditions existing with the valve in the positionshown in Fig. 8 establishes a similar result. Thus the pressure decreasefrom port P to port A in each channel C produces a clockwise torque.Compensating these torques is an opposing torque generated in operativechannel D by virtue of the shift in the center of pressure towards portA The torque generated thereby is in a counterclockwise direction. Itmay also be observed in connection with the above described theory thatfluid flow from ports A to P in Fig. 6 and from A to P in Fig. 8 resultsin moment arms which are larger than each of the moment arms associatedwith fluid flow in channels C. In this connection it may also be notedthat the pressure drop in channels D is a number of times larger thanthe pressure drop in each channel C.

The invention in its broader aspects is not limited to the specificmechanisms shown and described but departures may be made therefromWithin the scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chiefadvantages.

I claim:

1. A rotary hydraulic valve for selectively connecting one side of anactuator to a source ofsupply of liquid under pressure and the otherside of said actuator to a lower pressure outlet, said rotary hydraulicvalve comprising a cylindrical housing and a rotor rotatable within saidcylindrical housing, said cylindrical housing having two opposed inletports, two opposed low pressure outlet ports and two pairs of opposedports for connection one pair to each side of said hydraulic actuator,said rotor having channels disposed between lands arranged so as to becapable of closing said two pairs of opposed ports, the relativepositions of said channels and all said ports being such that when thevalve is open both high pressure inlet ports are connected to acorresponding pair of said pairs of opposed ports but only one of theother said pair of opposed ports is connected to one low pressure outletport at any one time.

2. A valve as defined in claim 1, wherein said channels each have aconcave arcuate form in the direction from land to land.

3. A valve as defined in claim 1, wherein the ports are so arranged thatthe angles between the center line of '4 ing one side of an actuator toa source of supply of liq- -uid under pressure and the other side ofsaid actuator to a lower pressure outlet, said rotary hydraulic valvecomprising a cylindrical housing and a rotor rotatable within saidcylindrical housing, said cylindrical housing have two opposed inletports, two opposed low pressure outlet ports and two pairs of opposedports for connection one pair to each side of said hydraulic actuator,said rotor having channels disposed between lands arranged so as to becapable of closing said two pairs of opposed ports, the relativepositions of said channels and all said ports being such that when thevalve is open both high pressure inlet ports are connected to acorresponding pair of said pairs of opposed ports but only one of theother said pair of opposed ports is connected to one low pressure outletport at any one time, a plurality of said lands having surface areaslarger than other of said lands.

5. A valve as defined in claim 4 in which a pair of adjacent lands havesurfaces larger than other of said lands.

6. A valve as defined in claim 4 in which the volumes of one of saidchannels is difierent from other of said channels.

7. A valve as defined in claim 4 in which the channels associated withsaid low pressure outlet ports are each smaller than the channelsassociated with said high pressure ports.

References Cited in the file of this patent UNITED STATES PATENTSMekelburg et al. Dec. 18, 1956

